1. Technical Field.
This invention relates to mechanical coupling devices in general, and to mechanical coupling devices that are hand operable in particular.
2. Background Information.
Presently available coupling devices for selectively coupling shaft sections typically utilize an attachment mechanism such as an independent pin or key, screw threads, or a spring-loaded cylindrical or spherical shaped button mounted. A problem with coupling devices that utilize an independent pin or key is that the pin or key is often misplaced and/or requires a tool for implementation. A problem with coupling devices that utilize screw threads is that if the application requires that the shaft be rotated, the threaded sections can become detached from one another. If a shaft section becomes decoupled in an inaccessible area (e.g., a chimney), the shaft section remaining in the inaccessible area can present a significant problem.
Presently available coupling devices that utilize spring-loaded cylindrical or spherical shaped buttons solve some of the problems associated with screw threads and pins, but they too have disadvantages or are limited in application. Spring-loaded cylindrical or spherical shaped button-type couplings are typically utilized on applications where the shafts to be coupled are thin wall type shafts; e.g., vacuum shaft sections. The button is mounted on the male portion of the coupling and is biased outwardly. Inserting the male portion of the coupling into the female portion causes the button to be deflected inwardly, thereby allowing the male portion to be received within the female portion. When the outwardly biased button encounters an aperture within the female portion, the button extends outwardly through the aperture in the thin wall of the female portion and thereby positively couples the male and female portions and the shafts attached thereto. The male and female portions can be decoupled by applying pressure from a finger on the button, pushing the button inwardly below the inner surface of the female portion. This manner of decoupling works well for thin wall applications because skin from the operator""s finger will extend a distance into the aperture provided sufficient pressure is applied. The distance the finger extends into the aperture is substantially equal to or greater than the wall thickness of the female coupling portion.
Applications that require a stronger shaft and coupling device, particularly those where rotational torque is transmitted through the shaft, often utilize a thick wall coupling device. Some existing thick wall coupling devices utilize a spring mounted cylindrical button in the same manner as that described above. One problem with using a cylindrically shaped button in a thick wall coupling device application is that it becomes difficult or impossible to depress the button by finger (hereinafter xe2x80x9cfingerxe2x80x9d shall be defined as any digit on a hand including a thumb) below because the finger skin only extends a limited amount into the aperture. Consequently, the finger by itself is unable to depress the button inwardly a distance sufficient to disengage the button from the aperture within the female portion. This is particularly true in applications where the operator is wearing work gloves that are less compliant than skin. In such cases, it becomes necessary to use a tool to depress the button the required distance. Another problem with using a cylindrical button in a cylindrical thick wall coupling device is that the button extending between the male and female portions carries any load torsionally or axially transmitted between shaft sections. As a result, the ability of the shaft sections to transmit a load is likely to be limited by the strength of the cylindrical button.
What is need therefore, is a coupling device that does not utilize independent loose parts, one that will not unintentionally decouple, one that is easily hand operated, and one that provides a favorable torsional loading capability.
It is therefore, an object of the present invention to provide a unitary coupling device that will not unscrew, one that can be hand operated, and one that provides a favorable torsional loading capability.
According to the present invention, a shaft coupling device is provided that includes a first portion, a second portion, a plunger, and a spring. The first portion includes a female mating section and a shaft mounting section. The female mating section includes a first cavity surrounded at least in part by a wall. An aperture extends through the wall. The second portion includes a male mating section and a shaft mounting section. The male mounting section is sized so as to be receivable within the cavity of the female mating section. The male mounting section includes a second cavity surrounded at least in part by a wall, and an aperture extending through that wall. The plunger has a body with a width and a length, and the length is greater than the width. A flange is attached to one end of the body. The plunger is disposed within the second cavity of the male mating section and the body of the plunger extends through the aperture within the wall of the male mating section. The spring is disposed within the cavity of the male mating section, and acts between the wall of the male mating section and the plunger. In a coupled state, the male mating section is received within the cavity of the female mating section and the body of the plunger extends through the apertures within the male and female mating sections and is biased in place by the spring.
According to one aspect of the present invention, the female mating section includes a cutout that intersects with the aperture disposed within the wall of the female mating section. The cut out is positioned so that base of the cutout substantially intersects with the inner wall surface that defines the cavity.
An advantage of the present coupling device is that it can be readily hand operated. The extended length of the present plunger provides a surface long enough so that the curvature of a finger will enable the finger to depress the plunger a distance substantially equal to or below the inner wall surface of the cavity of the female mating section, thereby enabling decoupling of the first and second portions of the coupling device without the use of a tool. In addition, in those embodiments that include the above-described cutout, the cutout enables the finger to be oriented perpendicularly relative to the length of the plunger when depressing the plunger. The depth of the cutout permits the operator""s finger to depress the plunger below the inner wall surface of the cavity of the female mating device, thereby enabling decoupling of the first and second portions of the coupling device without the use of a tool.
Another advantage of the present coupling device is the load capacity it provides, and in particular the torsional load capacity it provides. Existing coupling devices that utilize a cylindrical button extending between cylindrical male and female portions have limited torsional load capacity relative to the present coupling. Specifically, the extended length of the present plunger and the increased wall surface area against which it acts within the apertures disposed in the male and female mating sections, serve to distribute the load along the length of the plunger and thereby minimize the load per unit area. As a result, the coupling device can accommodate a higher magnitude load than is possible with present button-type coupling devices. This attribute is particularly important for applications where the coupling is driven by a power source other than by hand. For example, in many chimney, duct, or pipe cleaning applications it is desirable to use a cleaning head attached to a shaft that is driven by a rotary device such as a drill or other drive motor. Since drive motors can impart significantly more torque than can be applied by hand, it is critical that the coupling between shafts and/or between a shaft and a cleaning head be able to accommodate the additional torque.
Another advantage provided by the present coupling device is that the two portions of the coupling device will not unscrew from one another or otherwise uncouple during use. A person of skill in the art will recognize the significant problems can arise should, for example, a cleaning tool, become uncoupled in a blind application such as a chimney, flue, or vent.
Another advantage of the present coupling device is that it does not require a loose independent piece such as a pin or screw to couple two shaft lengths.
These and other objects, features, and advantages of the present invention will become apparent in light of the detailed description of the present invention.